Experimental evaluation of plutonium-239 spike for determining plutonium concentration by isotope dilution-thermal ionization mass spectrometry

Abstract

The use of 239 Pu as a spike in isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) for determining the plutonium concentration in irradiated fuels is demonstrated. The method is based on the high precision better than 0.1% determination of the 240Pu/ 239Pu atom ratio in the sample, the spike, and the spiked mixture. The precision and accuracy of the results obtained on different plutonium samples using a 239Pu spike are compared with those obtained using a 242Pu spike. A mean precision of 0.1–0.2% is achieved using a 239Pu or 242Pu spike and a factor close to unity is obtained for the ratio ID-TIMS ( 239Pu)/ID-TIMS ( 242Pu). This study provides a viable alternative spike material to those laboratories which do not have access to enriched 242Pu, which is generally used in determining the plutonium concentration by ID-TIMS, and at the same time, offers certain advantages over the use of a 242Pu or 244Pu spike.